We propose to conduct a prospective cohort study to determine whether infants born to women dually infected with both the Human Immunodeficiency Virus Type I(HIV- 1) and Toxoplasma are at increased risk for congenital toxoplasmosis. As opposed to the usual clinical situation where congenital Toxoplasma infection occurs only when the mother is primarily infected during gestation, women latently infected with Toxoplasma and immunosuppressed by concurrent HIV-1 infection have been observed to deliver infants with congenital toxoplasmosis. The background rate of congenital toxoplasmosis in the United States is low (1/1000 to 1/3000 live births). Considering that a sizable percentage of HIV-1 infected mothers may be seropositive for Toxoplasma(38% of 471 Haitian women screened to date) and that many of these may have deficient cell-mediated immunity, reactivation of encysted organism associated with intermittent or chronic parasitemia may be a recurrent event. The frequency of transplacental transmission of Toxoplasma in this situation therefore may exceed the background rate of congenital infection secondary to primary infection in seronegative women. This study will compare the rate of congenital Toxoplasma infection in a group of infants born to women infected with both HIV-1 and Toxoplasma with the rate of congenital infection in a group of infants born to women infected with Toxoplasma only. These rates will also be compared with the rate of acquired Toxoplasma infection in infants not at risk for congenial toxoplasma infection.